Protoberberines dimerization

In a pair of back-to-back papers, the author and co-workers first reported the isolation and characterization of thalibealine (70), a novel tetrahydro-protoberberine-aporphine dimeric alkaloid from Thalictrum wangii,143 That report was followed by a paper reporting the synthesis of thalprezwalskinone (71) and a revision of the structure of that alkaloid.144... 

T. sultanabadense Stapf., a small plant that grows under the shade of rocks on the rocky mountain slopes of eastern Turkey, is a source of the dimeric bisbenzylisoquinoline alkaloids thalbadensine, hemandezine, and thalictine, and the monomeric alkaloids thalifoline (isoquinolone), berberine (protoberberine), and magnoflorine (aporphine). 

Perhaps the most well-known peroxidase-catalyzed reactions are those involving electron transfer, in which an aromatic substrate is oxidized in a mono-electronic oxidation up to its mono-radical, Eq. (1), which is capable of participating further in a variety of non-enzymatic reactions such as disproportionation, polymerization and electron transfer. These types of reactions are very common during the peroxidase-catalyzed oxidation of phenols and, in some cases, during the oxidation of alkaloids. For example, peroxidase is capable of dimerizing jatrorrhizine (IV) to 4,4 -bis-jatrorrhizine (V) in the presence of H2O2 (Scheme III) [50], Jatrorrhizine is a bioactive protoberberine alkaloid present in Colombo radix (Jatrorrhiza palmata) widely used in both oriental and western medicine. 

Benzylisoquinolines.—An extensive review of Thalictrum alkaloids has appeared. These include benzylisoquinolines, bisbenzylisoquinolines, isoquinolones, apor-phines, aporphine-benzylisoquinoline dimers, phenanthrenes, protoberberines, protopines, pa vines, and isopa vines. The alkaloids of the Lauraceae have also... 

Dimeric protoberberinium salts have been obtained by reaction of dihydro-protoberberines with formaldehyde, most probably by the mechanism indicated below... 

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